A Michigan State University researcher has found that high blood pressure, a leading cause of heart attacks and strokes, can be lowered significantly by using portable air filters that remove tiny indoor air particles known to increase risk of cardiovascular issues.
The study, published in JAMA Internal Medicine, found that on average the filters lowered blood pressure by an amount similar to if a person increased his or her exercise or reduced salt intake, said Masako Morishita, the study’s lead author and an associate professor in the College of Human Medicine.
Lowering systolic blood pressure even a small amount, around 1-mm Hg, could prevent an estimated 10,000 coronary heart disease deaths each year in the United States.
Morishita’s study showed for the first time in the United States that the use of HEPA filters decreased systolic blood pressure by an average of 3-4 mm Hg.
“The takeaway message is that a simple intervention using a fairly inexpensive filter can reduce blood pressure,” said Morishita, an internationally recognized exposure science expert. “This is an important finding, because hypertension is the leading cause of death worldwide.”
The study, supported by a grant from the National Institute of Nursing Research, involved 40 nonsmokers in a low-income residential building for senior citizens located near a major highway and an industrial area in Detroit.
A portion of the residents were provided low-efficiency, HEPA-type filters, while others were given high-efficiency ones or sham filters that didn’t clean the air at all. HEPA, or high-efficiency particulate air, filters remove tiny particles of dust, dirt and soot known as PM2.5.
Participants wore monitors that measured their PM2.5 exposure and researchers measured their blood pressure before and after the filters were provided.
Compared to the sham filter, the low-efficiency filters reduced exposure to tiny air particles by 31 percent, and the high-efficiency ones by 53 percent. More significantly, after only three days, participant blood pressure also had dropped, regardless of which of the two filters were used.
Morishita said she wasn’t surprised to see such a rapid improvement in blood pressure, since previous studies have shown that inhaling the tiny particles can increase it within hours. Breathing the dirty air apparently triggers a rise in blood pressure by disrupting the nervous system or triggering inflammation, she said.
The filters also may have been particularly beneficial in lowering blood pressure for study participants who were obese, but Morishita advises that further research is needed.
Health experts estimate that roughly 88,000 deaths per year in the United States are due to PM2.5 exposure. The World Health Organization estimates about four million deaths worldwide are caused by exposure to the tiny air particles annually as well.
“I think this is a very important study,” said Bengt Arnetz, chair of the Department of Family Medicine. It not only adds to the understanding of hypertension, but demonstrates why physicians should be aware of how environmental exposure affects their patients. The same inflammation that causes blood pressure to increase is a factor in many other diseases, including cancer, he said.
Morishita has applied for a grant to conduct a follow-up study with HEPA filters to verify if the lower blood pressure persists for a longer period and to check patients for inflammatory markers and other indicators of cardiovascular disease.
Eventually, she hopes to conduct a long-term study to determine if the filters not only help reduce blood pressure, but lower the risk of heart attack and stroke.
Co-authors on the study included University of Michigan researchers Robert Brook, Sara Adar and Catherine Spino, as well as Rosemary Ziemba from Community Health Nursing.